Peel and seed the apples and cut them into large pieces. Place the apple pieces, lemon juice, wine, brown sugar and raisins in a saucepan.
Slit open the vanilla bean and scrape out seeds with the tip of a paring knife. Add the seeds and the vanilla bean to the pan. Bring the mixture to the boil. Cover and cook over low heat for 4 to 5 minutes. The apples should be soft but still hold their shape.
Remove the pan from the heat. Remove the vanilla bean and drain the apples, reserving liquid. Stir the crème fraîche into the liquid and spoon onto serving plates.
Coarsely chop the walnuts. Mix with the apples and distribute among the serving plates.
Heat the Calvados over low heat, ignite a small amount in a soup or gravy ladle (see note below), one serving at a time, and pour over the fruit salad. Serve at once.